This invention relates to 20-high cluster mills used for the cold rolling of metal strip, and having a 1-2-3-4 roll arrangement as shown in U.S. Pat. Nos. 2,169,711; 2,187,250; 2,470,974; 2,776,586 and 4,289,013, such mills being commonly known as "Sendzimir" mills, "Z" mills or "Sendzimirs".
The invention is particularly concerned with improved additional means for shaping the profile of the rolling mill to the profile of the strip, in order to achieve uniform elongation at every point across the width of the strip, thus enabling uniform tension distribution, and strip of good flatness.
An exemplary cluster mill of the type to which the present invention is directed is shown in FIG. 1. A pair of work rolls 12, through which the strip 32 passes during the rolling process is supported by a set of four first intermediate rolls 13, which are in turn supported by a set of six second intermediate rolls consisting of four driven rolls 15 and two non-driven, or idler rolls 14. The second intermediate rolls are supported in their turn by eight backing assemblies (see also FIG. 2) each consisting of a plurality of roller bearings 30 mounted upon a shaft 18, the shaft 18 being supported at intervals along its length by saddles, each saddle consisting of a ring 31 and a shoe 29 (these parts being bolted together). The saddle shoes 29 rest in a series of partial bores in a mill housing 10, of the type generally described in U.S. Pat. No. 3,815,401.
FIG. 1 is an elevational view of the cluster mill as seen from what is usually referred to as the "front" of the mill or the "operator's side" of the mill. It is normal practice to label the backing assemblies and their components as shown in FIG. 1, where the leftmost upper assembly is labelled "A", and working clockwise around the mill, the remaining assemblies are labelled "B" through "H". This naming convention will be followed in this specification and the claims, being applied to both the backing bearing assemblies and their constituent parts.
In general, all of the saddles on all eight backing assemblies include eccentrics, which are keyed to the respective shafts, and provided with bearing surfaces on their outside diameters, which engage with bores in the saddle rings 31, such that rotation of the respective shafts will cause radial motion of shafts and of bearings mounted thereon.
In the case of assemblies A, D, E, F, G and H, the saddles are known as "plain saddles" and eccentrics 23 mount directly within saddle rings 31, and slide within these rings as the respective shafts are rotated. In such cases, because the friction between the sliding surfaces is high, shafts will not be adjusted under load (i.e. during rolling). A, D, E and H shafts eccentrics are known as the "side eccentrics". Rotating these shafts is used to adjust the radial position of their bearings to take up wear on rolls 12 through 15.
F and G shaft eccentrics are known as the "lower screwdown eccentrics". Rotation of F and G shafts and their eccentrics can be used to take up for roll wear also, but is more frequently used to adjust the level of the top surface of lower work roll 12. This is known as "adjusting the pass line height" or "pass line adjustment".
In the case of assemblies B and C, the saddles are known as "roller saddles". For small mills (which have no crown adjustment) the construction is the same as for the plain saddles, with the exception that a single row of rollers is interposed between the outside of each eccentric and the inside of the mating saddle ring 31. This enables the shafts and the eccentrics keyed thereto to roll within saddle rings 31. The friction is then sufficiently low for adjustment to be made under load. This adjustment is known as the "upper screwdown" or "screwdown" and is used to adjust the roll gap (gap between work rolls 12) under load. The method adopted, as is well known in the art, is to use two double racks 21, one engaging gears 22 on shafts B and C at the operator's side, and one engaging gears 22 on shafts B and C at the drive side (see FIG. 2). Each double rack is actuated by a direct acting hydraulic cylinder 20, and a position servo is used to control the position of the hydraulic pistons, and so control the roll gap.
For larger mills (and for some newer small mills) provision is made for individual adjustment of the radial position of the shaft, bearings and eccentric rings at each saddle position. This adjustment is known as "crown adjustment" and the prior art construction used to achieve it is shown generally in FIGS. 3 through 6.
On the B and C saddles 20, the saddle rings 31 are provided with a larger diameter bore 32, so that a second set of rollers 33 and a ring 34 (the outside diameter of which is eccentric relative to its inside diameter) can be interposed between saddle ring 31 and rollers 37. Rings 34 are known as "eccentric rings". A gear ring 38, having gear teeth 40, is mounted on each side of each eccentric ring 34, and rivets 39 are used to retain gear rings 38, eccentric 23, eccentric ring 34, saddle ring 31 and shoe 39, with two sets of rollers 33 and 37, together as one assembly, known as the saddle assembly.
As shown in FIGS. 3 and 4, a double rack 41 is used at each saddle location, to engage with both sets of gear teeth 40 on each gear ring 38 on both B and C saddle assemblies. A hydraulic cylinder 42, or motor driven jack, is used at each saddle location in order to translate the rack 41. In the example of FIGS. 2 and 6, seven individual drives would be provided, one at each saddle location. These are known as "crown adjustment" drives. If one drive is operated, its respective double rack 41 moves in a vertical direction, rotating the associated gear rings 38 and eccentric rings 34. This causes radial movement of eccentrics 23 on shafts B and C at the saddle location on which the eccentric rings rotate, and a corresponding change in the roll gap at that location, shafts 18 bending to permit this local adjustment.
Although independent drives are provided at each saddle location, the adjustment is not truly independent, due to the transverse rigidity (i.e. resistance to bending) of each shaft 18.
Copending application Ser. No, 071,917,157, filed Jul. 29, 1992, in the names of Michael G. Sendzimir and John W. Turley and entitled IMPROVED PROFILE ADJUSTMENT FOR CLUSTER MILLS, teaches various embodiments of backing bearing assemblies and second intermediate idler rolls characterized by greatly reduced transverse rigidity enabling more complex roll gap profiles to be achieved. The teachings of this copending application are adaptable to the present invention, as will be apparent hereinafter, and are incorporated herein by reference.
The above-noted copending application states that such double eccentrics could also be used to provide crown adjustment on backing bearing assemblies F and G, but that this has never been done, due to the difficulties of access to the crown adjustment drive which would normally need to be attached to the bottom of the mill housing, in an area which is flooded with oil during mill operation, and is very uncomfortable for maintenance personnel to work in due to tight space, slippery surfaces and constant dripping of oil from overhead.
It is the object of the present invention to provide a profile adjustment drive system operating via eccentric rings on the F and G backing assemblies, which is not subject to the accessibility problems of prior art drive systems.